一种具有声低通滤波特性的无源零差光纤水听器

报道了一种新颖的具有抗混叠功能的无源零差迈克耳孙型光纤水听器.它由一个普通的芯轴型光纤水听器和一个圆柱型亥姆霍兹共振器构成.在驻波罐中对其声压相位灵敏度频响进行了测量,结果表明该光纤水听器具有较好的声低通滤波特性,能有效地抑制声信号中的高频成分,从而实现抗混叠滤波.该光纤水听器的低频声压相位灵敏度主要由传感光纤长度和弹性增敏层的物理特性决定,约为-159 dB(0 dB=1 rad/μPa).在1150 Hz附近出现了一个共振峰,这主要由圆柱型亥姆霍兹共振器的声学特性决定.1150～2280 Hz频段内的灵敏度衰减率约为50 dB/倍频程,1500 Hz以后的灵敏度衰减量大于10 dB.这对于提高我国未来声纳系统的抗干扰能力具有十分重要的意义.     

台风对沿海地区气溶胶光学特性的影响分析

利用CE317太阳辐射计对2005年第19号台风登陆前后期问(9月29 H至10月6日)进行观测实验,采用Langley法分析台风对中国大陆沿海地区气溶胶光学特性的影响.指出台风过后气溶胶光学特性明显发生改变,气溶胶大粒子数增多,小粒子数减小.气溶胶光学厚度、Angstr(o)m波长指数α和大气混浊度系数β为测量期间最低分别为0.132(550 nm处),0.861和0.079.同时利用实验期间APS3321空气动力学粒度仪分析的气溶胶单位体积数粗细质粒所占比重、气溶胶粒子尺度谱分布和实测的日际气溶胶粒子数浓度对实验分析结果.α,β进行对比,发现它们之间的一致性很好.     

对数饱和非线性介质中的自洽多模高斯孤子解

通过解对数饱和非线性介质中光场满足的非线性薛定谔方程,得到一组厄米-高斯型的自洽多模解.在借鉴了R.G.Glauber的相干态理论的基础上,合理假设这组解在非线性介质中呈泊松分布,进而得到了在对数饱和非线性介质中存在高斯孤子的结论,并获得高斯孤子解、非线性系数与泊松参量三者之间的关系.该关系说明,若在介质中存在高斯孤子解,其非线性系数必须满足条件a≥1.当α=1,在介质中仅存在单模高斯孤子,其光斑尺寸必须满足的条件W=1/k n0/n2.在该条件下,以"束腰"注入介质中的高斯光束才可以在保持其光斑尺寸不变的情况下传输,否则光斑尺寸会存在一定的振荡.而振荡方式、振荡范围(表示光斑尺寸展宽或压缩及大小)与输入光束光斑尺寸及其一次导数有直接关系.     

5,10,15-三(五氟苯基)Corrole及其相似卟啉化合物的光物理特性

采用稳态和时间分辨的瞬态光谱技术对比研究了一种Corrole化合物5,10,15-三(五氟苯基)Corrole(FtsTPC)和一种卟啉化合物5,10,15,20-四(五氟苯基)卟啉(F20TPP)的光物理特性.结果表明:F15TPC的B带吸收峰较宽而F20TPP的强而窄,F15TPC的Q带有两个吸收峰而F20TPP有四个.F15TPC的荧光量子产率为0.15,荧光寿命为4.8 ns,F20TPP的荧光量子产率为0.05,荧光寿命为11.1 ns;与F20TPP相比F15TPC具有发光效率高、荧光寿命短的特点.F15TPC具有较大的发光速率常数和无辐射跃迁速率常数,这可能是由于F15TPC少了一个氟代苯基,致使其发色团本身的电子结构发生变化所致.另外空间结构的不对称性和非共面性也对其光物理性质有影响.     

基于菲涅耳透镜阵列的红外气体传感器

菲涅耳透镜同时具有分光与会聚特性, 且体积小、重量轻和易复制, 使其在光谱检测中得到逐步应用, 但典型光谱成像仪采用菲涅耳透镜沿光轴扫描的方法来获得连续谱线, 不利于光谱仪的稳定性。考虑到气体探测需求, 选用多通道方式来获得多光谱, 提出了一种基于菲涅耳透镜阵列的新型红外气体传感器, 可实现吸收波长在3～5 μm的CO2,CO,CH4,SO2气体的实时检测。利用球面波的传输理论和瑞利判据, 推导了菲涅耳透镜光谱分辨率与透镜结构参数之间的函数关系, 并以光谱分辨率小于50nm为性能指标, 对1μm工艺的8台阶菲涅耳透镜阵列的结构参数进行了计算和误差分析。结果表明, 透镜阵列所需焦距为47.84 mm, 平均数值孔径大于0.4。     

Propagation of Four-Petal Gaussian Beams in Turbulent Atmosphere

An analytical expression for the average intensity of four-petal Gaussian beams in turbulent atmosphere is derived. Studies show that in turbulent atmosphere, the contour lines of four-petal Gaussian beams with lower order N evolve into a number of petals with the increase in propagation distance, the contour lines with higher order N can reserve four-petal distribution at longer propagation distance than that with lower order N. These properties are similar to those in free space. However, with further increases of the propagation distance, the contours lines in turbulent atmosphere are different from those in free space.     

Laser-Duration Dependence of Emission Properties of High-Order Harmonic Generation

Quantitative investigations are made for the laser-duration dependence of the emission properties of high-order harmonic generation （HHG）. HHG emission properties produced by few-cycle lasers show some useful characteristics. The cutoff energy is less than that by laser for infinite duration. The single energy distribution pulse decreases much faster than its duration as the laser duration grows. A two-cycle laser with carrier-envelope phase of 0° can produce a single distribution pulse peaked at the laser carrier phase 1.22 rad and spanned 1.18 rad with the cutoff energy 2.9Up ＋ Ip and a bandwidth 0.63Up, where Up is the ponderomotive potential of the laser field and Ip is the atomic ionization potential.     

Microstructure and Optical Properties of AgxO Prepared by Direct-Current Magnetron-Sputtering Method

Two series of AgxO films are prepared on glass substrates by dc magnetron-sputtering method at room temperature and 90℃ under different oxygen to argon gas ratio （OAR） conditions. The mierostrueture is investigated by XRD and SEM in order to obtain the information on the component evolution of AgO＋Ag2O to Ag2O. Its optical properties are investigated by reflectance and absorption spectroscopy to extract the information on metallic and dielectric behaviour evolution of Ag2O, AgO and silver particles and the interband transition. The results indicate that the AgxO film prepared at room temperature is mainly made up of AgO and Ag2 O clusters while Ag2O is the primary component of AgxO prepared at 90℃. The AgxO film mainly consisting of the primary component shows indirect interband transition structure occurring at 2.89eV. Combination of increasing OAR and substrate temperature is an effective method to lower the threshold of thermal decomposition temperature of AgxO and to deal with the bottleneck of short-wavelength optical and magneto-optieM storage.     

A Simple Route of Morphology Control and Structural and Optical Properties of ZnO Grown by Metal-Organic Chemical Vapour Deposition

Employing the metal-organic chemical vapour deposition （MOCVD） technique, we prepare ZnO samples with different morphologies from the film to nanorods through conveniently changing the bubbled diethylzinc flux （BDF） and the carrier gas flux of oxygen （OCGF）. The scanning electron microscope images indicate that small BDF and OCGF induce two-dimensional growth while the large ones avail quasi-one-dimensional growth. X-ray diffraction （XRD） and Raman scattering analyses show that all of the morphology-dependent ZnO samples are of high crystal quality with a c-axis orientation. From the precise shifts of the 20 locations of ZnQ （002） face in the XRD patterns and the E2 （high） locations in the Raman spectra, we deduce that the compressive stress forms in the ZnO samples and is strengthened with the increasing BDF and OCGF. Photoluminescence spectroscopy results show all the samples have a sharp ultraviolet luminescent band without any defects-related emission. Upon the experiments a possible growth mechanism is proposed.     

Nitrogen Dioxide Sensing Properties and Mechanism of Copper Phthalocyanine Film

Copper phthalocyanine film, a p-type organic semiconductor, is synthesized by vacuum sublimation and its surface morphology is characterized by SEM. A silicon-based copper phthalocyanine film gas sensor for NO2 detection is fabricated by MEMS technology. The results show that the resistance and sensitivity of copper phthalocyanine film decrease obviously as the NO2 concentration increases from Oppm to lOOppm. However, the sensitivity nearly keeps a constant of O. 158 between 30 ppm and 70 ppm. The best working temperature of the gas sensor is 90℃ for NO2 gas concentrations of lOppm, 20ppm and 30ppm, which is much lower than that of general metal oxide gas sensor.